Reviews from critics were mixed. On
Rotten Tomatoes, the film has an approval rating of 63% based on 16 reviews, with an average rating of 5.45 out of 10.
The Monthly Film Bulletin wrote: "A plot has been crudely put together with the incongruously clearcut and matter-of-fact tone of a crime thriller ... and the three personalities slotted in at the appropriate places. To justify two of the stars, the theme of vampirism slides, ominously and unnecessarily, in and out of the film, and the creation of a whole race of man-made monsters is now accomplished by a more advanced science than Dr. Frankenstein's ... Vincent Price, hypersensitive recluse and dabbler in the occult, is the menacingly affable director of the clinic where events, and the new supermen, all begin. Not surprisingly, the triumvirate have little room to manoeuvre inside the tight fit of their functional clichés: Peter Cushing has the least opportunity (little more than a bit part), while Christopher Lee disappears into a greying nonentity of a civil servant, failing to emerge even with the final revelation of masked depravity. Vincent Price inimitably delivers the most banal dialogue with a disconcerting relish, though the giveaway decadence of Dr. Browning's living quarters, keyed to a pretty shade of pastel pink, would have provoked a creeping horror in Roderick Usher."
Howard Thompson of
The New York Times wrote that the film "tools along intriguingly for a while with some genuine possibilities before taking a nosedive", when it "ends up in still another mad scientist's lair".
Variety wrote that the script "has almost as many holes as the assorted victims of the action. However, such criticism is completely irrelevant to the film's gripping momentum of horror."
Roger Ebert of the
Chicago Sun-Times gave the film two stars out of four, calling it "ridiculous", yet "impossible to dislike because they ask only that you share their sense of the absurd. The fascinating thing about this one is that it makes absolutely no sense at all until maybe the last 10 minutes. None."
Gene Siskel of the
Chicago Tribune gave the film one star, calling it "a violent and sick film ... that begs to be included in our annual worst twenty list."
Kevin Thomas of the
Los Angeles Times called the film "a superb piece of contemporary horror, a science fiction tale possessed of a credibility more terrifying than any of the Gothic witchery of
''Rosemary's Baby'' ... It's one of those movies where you have no idea what's going on until the end, but once there, there's no letdown." ==References==